The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs. Each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs.
Over the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometric size has decreased. The thicknesses of semiconductor device structures (e.g., chips or packages) have decreased as well.
However, since feature sizes continue to decrease, fabrication processes continue to become more difficult to perform. Therefore, it is a challenge to form reliable semiconductor devices at smaller and smaller sizes.